Decoding Analog Signals with PCM/QAM - Help Needed

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Discussion Overview

The discussion revolves around the conversion of analog signals to digital formats, specifically focusing on decoding fax information that is modulated using Pulse Code Modulation (PCM) and Quadrature Amplitude Modulation (QAM). Participants are exploring the technical requirements and challenges involved in developing a program for this purpose.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • One participant seeks assistance in decoding analog signals modulated with PCM/QAM to extract fax data.
  • Another participant suggests the necessity of an Analog-to-Digital Converter (ADC) and Digital Signal Processing (DSP) knowledge, asking for more details about the system.
  • A participant describes their setup of recording analog signals from a phone line and expresses difficulty in demodulating these signals to retrieve digital data.
  • Some participants recommend looking for documentation on fax modulation and coding schemes, while others suggest educational resources or products that could aid in the process.
  • There is a mention of the complexity involved in the task, with one participant indicating that a comprehensive understanding of digital signal processing is required.
  • Another participant emphasizes the importance of having the right tools and compatibility with programming languages for successful implementation.
  • One participant acknowledges their understanding of QAM and PCM but struggles with practical application and finding relevant documentation.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and expertise regarding the topic, with no consensus on the best approach to decode the analog signals. Some participants suggest educational resources, while others focus on practical implementation challenges.

Contextual Notes

Participants mention limitations in their current knowledge and resources, highlighting the need for specific documentation on fax modulation and the complexities involved in converting analog signals to digital formats.

IT_GE
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from analog to digital(PCM/QAM)

I want to convert analog to digital.

I am recording analog signals in my firm and i want to make a programm witch helps me to decode fax informations.

if you know how to decode this analog signals witch is modulated with PCM/QAM, please help me.
 
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Obviously, you'll need an ADC and a DSP. If you could tell us more about your system, we can be more helpful. Of course, you might want to consider hiring a contractor with the appropriate skills.

- Warren
 
ok

now i have connected with line in cable to the my phone cable. i am sending faxes to another line and recording it's analog signals with sound forge.

i have documentation about qam but i can't get any digits from this vawe files.

i am searching algorithm how to demodulate analog signals and get fax data as tiff, bmp or jpg or another fortmat
 
This product might help you: http://www.vectronics.com/vectronics/products.php?prodid=VEC-1613
 
Last edited:
no
I not need any products.
I want to write a program which will be integrated in my system.
 
i am parallel connected to the analog phone line witch is using to send/receive faxes.
i am recording this analog signals in vawe/pcm format.
i know how fax protocol is working, but i don't know how modulates digital signals to analog... and how to demodulate analog signals and get digital data.

i am askign you...
if you have any documentation about fax modulation or you can help me, please make it now.
 
IT_GE:

You're essentially asking us to give you a university-level education on signals and digital signal processing. It's quite simply outside the bounds of what we can teach you on an online forum. I suggest buying some books, or taking some classes. You need to learn quite a bit before you can do what you're trying to do.

- Warren
 
ok

chroot

i know how analog and digital signals work.

but i need documentation about fax modulation.

i can't find this documentation.

if you know where i can get this documentation please tel me.
 
IT_GE:
Goto Google and look under Facsimile Coding Schemes
I think you will find all the information you need.
 
  • #10
IT_GE:
if you know how to decode this analog signals witch is modulated with PCM/QAM, please help me.
-------------------------------------------------------------
PCM=PULSE CODE MODULATION
QAM=QUADRATURE AMPLITUTE MODULATION
A FAX MODEM CONTAINS ALL THE HARDWARE TO CONVERT THE
SIGNALS FROM ANALOGUE TO DIGITAL,use a programming language
to capture-decode-manipulate-present digital data,there's very little
decoding left to do,just get fax protocal details to give an idea what
you have to do with the software
 
  • #11
i suggest you buy from a vendor that provides you with complete
tools--hardware-drivers-libs and make sure your programming language
is compatible with those
 
  • #12
ok
thank
i know what is qam and pcm.
i have files witch is recorded as pcm wav file.
i know fax is using qam for modulation/demodulation of digital data to/from analog sygnal.
i know how to get tiff images from the digital data, but i don't know how to connvert this analog signals.
i have documentation about modulation, but it not like the really situation and not works properly.
i searched this info in google but no answer.
 

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